When the man reaches the other end of the barge, the center of mass will,
by symmetry, be 11.25 meters to the right of the midpoint of the barge. But,
since the position of the center of mass cannot move, this means the barge
itself must have moved a distance of 11.25 + 11.25 = 22.5 meters to the left.
- Let the time it takes the man to walk across the barge be denoted by t;
then. In this amount of time, the barge moves a distance of 22.5
meters in the opposite direction, so the velocity of the barge is